Gaston Tarry (September 27, 1843 - June 21, 1913) was a French mathematician. Born in Villefranche de Rouergue, Aveyron, he studied mathematics at high school before joining the civil service in Algeria. He pursued mathematics as an amateur, his most famous achievement being his confirmation in 1901 of Leonhard Euler's conjecture that no 6×6 Graeco-Latin square was possible.